Adjustable permanent magnet



Jan. 5, 1965 E. A. STEINGROEVER 3,

ADJUSTABLE PERMANENT MAGNET Filed May 16, 1962 2 Sheets-Sheet l 1965 E. A. STEINGROEVER 3,164,756

ADJUSTABLE PERMANENT MAGNET Filed May 16, 1962 2 Sheets-Sheet 2 %RJK United States Patent Office 3,164,756 Patented Jan. 5, 1965 V ADJUSTABLE PERN IANENT MAGNET Erich A. Steingroever, Bonn, Germany, assignor to Elektro-Physik Hans Nix & Dr. Ing. Steingroever, Cologne- Niehl, Germany I Filed May 16, 1962, Ser. No. 195,129

3 Claims. (Cl. 317159) I This invention relates to an adjustable permanent magnet whose magneticfiux may be initiated and selectively reversed inside an air. gap defined .by-suitably disposed soft iron conductor members.

In prior art adjustable permanent magnet systems, one or more cylindrical magnets, which are cross magnetized; are arranged rotatably between soft iron poles, the cylindrical surfaces of the magnets being connected to the soft iron members. By a rotation of the magnets around their axis the magnetic flux is adjusted relative to the soft iron poles. However, this arrangement of adjustable permanent magnet systems is not adapted. for obtaining high magnetic field forces and is not suitable for using large air gaps, because the diameter of the cylindrical magnets cannot be made very large. But in order to obtain a high magnetic field force in the air gap a substantial length of the magnet in the directionof magnetization is required in view of the known formula in which L is the magnetic length in the direction of magnetization, L is the length of the air gap, H is the field in the air gap, H is the field in the magnetic ma- The value H lieslin the, case of the usual'mag netic material at 300 600 oersted for alnico magnets,

terial.

or at 800 1200 oersted for oxide magnets.

According to the invention, itis possible to construct permanent magnet systems having large air gaps as well as high field forces in the air gap whilemantaining high ductor member 2 to the south pole S of the permanent magnet. The soft iron conductors are securely connected to each other through a non-magnetic support member 8 such as by soldering. For the purpose of regulating the magneticfield in the air gap the permanent 'magnet 1 is rotated around its longitudinal axis shown in dotted line in the drawing so that its poles make increasingly greater contact with the opposite soft iron conthe conductor members so that a field is present in ductor members. In a central position, aftera rotation of'90", the two poles N and S are short-circuited by the air gap. After a further rotation of 90 the pole N is connected to the conductor, member 2 and the pole S to the conductor member 3 so that the magnetic field present in the air gap is reversed with respect to the ini- 1 tial condition at the start of the rotation.

Referring now particularly to FIG. 3 of the drawing, the permanent magnet is composed of three parts 9, 1t) and 11, of which the parts9 and '10 are magnetized in the longitudinal direction of the system, while part 11 is magnetized *in a direction transversely of parts 9 and 10, With regard to FIG. 4 of the drawing there is shown an additional embodiment of the invention which permits a particularly easy actuation of the adjustable magnetic system. In this arrangement the permanent magnet sys-'.

tem consists of the two movable magnets 12 and 13 rotatable around the longitudinal axis and having an arcuate shape in cross-section. ,The magnets 12 and 13 are assembled to the non-magnetic intermediate members 14 and 15 to form a block, and are arranged slidably on the stationary iron feed back plate 16. The rotation is car ried out by means of a shaft 17 and a hand wheel or a drive wheel 18. The poles 19 and 20 are mounted a short distance above the movable part of the magnetic system andare supported bythe non-magnetic sleeve 21. Poles 19 and 20 are connected to each other by the nonmagnetic member 22. It will be observed that in. this arrangement only small friction forces are produced bevalues for L .Theinvention consists'in'providing an arrangement comprising a U-shaped one-piece'or composite permanent magnet which is rotatable around its longitudinal axis in such a manner that itspoles cover the connecting surfaces of the soft iron mmebers formingthe air. gap in a continuously. changing manner, In this case each pole of the permanent magnet may contact one or the other soft iron conductor member to a greater or lesser degree and induce it so that the field force in the air gap may be adjusted between any desired positive and negative values, thus also between 0 and each posi tive and negative value within the range that is possible in'the system; v j

An embodiment ofthe invention is illustrated inthe drawing in which: I V 7 FIG. 1 is a cross-sectional elevation of a magnet according to the invention,

FIG. 2 is a plan view of the magnet according to FIG. 1,

FIG. 3 is a cross-sectionalelevation of another em bodiment of a magnet according to theinventiom;

FIG-4 is still another embodiment of the magnet according to this invention, shown also in cross-sectional elevation.

Referringnowto FIGS. 1 and 2 of the drawing,'num eral 1 designates the U-shaped one-piece permanentm agnet having poles N and S and consisting for example of an alnico metal alloy. The soft iron conductor members 2 and 3 for the magnetic flux 4 indicated'in dotted lines are spaced from each other to define the air gap 5. Conductor members 2 and 3 are connected by contact surfaces 6 and 7 to the poles of the permanent magnet, 'conductor 3 being connected to the north pole N and contween the movable and the stationary parts of the magnetic system. As in the afore-mentioned embodiments the magnetic flux is indicated again in dotted lines and the magnetic field in the air gap 23' may be regulated by a rotation of the permanent magnets by means of the wheel 18 by 180 from the one maximum position through 0 to the Opposite maximum position.

During the movement of the permanent magnet parts of the adjustable magnet system reverse magnetization may occur in the areas which areimmediately adjacent the soft iron poles. This may be avoided according to the invention'by providing the movable permanent magnets with soft iron plates 24 which may be secured thereto in any suitable manner, such as by soldering or the I hom ogeneous fields, in moving-coil galvanometers, in

magnetic scales, inn-1 measurement, to record the hysteresis curve of magnetic materials or in core resonance iron work pieces. I

tests. It may also be used for nuclear resonance determinations." They may alsofind application as adhesion magnets, as tool or work holders in mechanical manufactures, or for assembling tensioning plates for 3 I claim: 7 l said permanent magnet unit for rotational displace- 1. An adjustable permanent magnet holding system ment thereof. comprising 2. An adjustable permanent magnet system according (1) a permanent magnet unit consisting of two parallel to claim 1 wherein the poles of the rotatable permanent permanent magnets having an arcuate shape in cross- 5 magnets opposite said stationary pole pieces are provided section and arranged'with their poles in opposite diwith soft iron plates in order to prevent a demagnetizarections, and non-magnetic means joining said magtion during the adjusting process. nets, said unit benig rotatable around its longitudinal 3. Adjust-able permanent magnet system according to axis, claim 1 wherein the permanent magnets are made of a (2) acylindrical stationary non-magnetic hoiising sur-fl 10 material having a magnetic pre-orientation.

rounding said unit, and a magnetic feed back plate, t said plate forming the bottom of said housing and. Refflfwces flied e of fills P2111311t Supportingsaid permanentmagnetunit, a UNITED STATES PATENTS (3) stationary feromagnetic pole pieces arranged toform a magnetic circuit vvith opposite poles of said 15 fg g 'T i tWo permanent magnets, and a non-magnetic spacing 2A71O67 f i 22 1949 member connecting said pieces to a unit, said pole Horvay 1952 pieces defining an air gap and being supported on 2888617 Baumet 1959 b said housing in close spaced relationship but out of n y direct contact with said permanent magnets, and 20 FOREIGN PATENTS -(4) manipulating means mechanically connected to 444,786 Great Britain Mar. 27, 1936 

1. AN ADJUSTABLE PERMANENT MAGNET HOLDING SYSTEM COMPRISING (1) A PERMANENT MAGNET UNIT CONSISTING OF TWO PARALLEL PERMANENT MAGNETS HAVING AN ARCUATE SHAPE IN CROSSSECTION AND ARRANGED WITH THEIR POLES IN OPPOSITE DIRECTIONS, AND NON-MAGNETIC MEANS JOINING SAID MAGNETS, SAID UNIT BEING ROTATABLE AROUND ITS LONGITUDINAL AXIS, (2) A CYLINDRICAL STATIONARY NON-MAGNETIC HOUSING SURROUNDING SAID UNIT, AND A MAGNETIC FEED BACK PLATE, SAID PLATE FORMING THE BOTTOM OF SAID HOUSING AND SUPPORTING SAID PERMANENT MAGNET UNIT, (3) STATIONARY FEROMAGNETIC POLE PICES ARRANGED TO FORM A MAGNETIC CIRCUIT WITH OPPOSITE POLES OF SAID TWO PERMANENT MAGNETS, AND A NON-MAGNETIC SPACING MEMBER CONNECTING SAID PIECES TO A UNIT, SAID POLE PIECES DEFINING AN AIR GAP AND BEING SUPPORTED ON SAID HOUSING IN CLOSED SPACE RELATIONSHIP BUT OUT OF DIRECT CONTACT WITH SAID PERMANENT MAGNETS, AND (4) MANIPULATING MEANS MECHANICALLY CONNECTED TO SAID PERMANENT MAGNET UNIT FOR ROTATIONAL DISPLACEMENT THEREOF. 